Method for drying sheet material



2 Sheets-Sheet 1 o MINTON METHOD FOR DRYING SHEET MATERIAL OriginalFiled Jan. 8.

Aug. 10 1926.

Y E N R O 1920 2 Sheets-Sheet 2 Aug. 10 1926.

INVENTOR OGDEN MIN TON fifi r A TTORNE Y Patented Aug. 10, 1926.

PATENT OFFICE.

OGDEN MINTON, OF GREENWIGH, CONNECTICUT.

METHOD FOR DRYING SHEET MATERIAL.

Application filed. January 8, 1920, Serial No. 350,236: Renewed July 8,1926.

The present invention relates to an apparatus and method for the dryingof paper and other sheet materials.

My improved method consists in passing the sheet material, which is tobe dried, into a vacuum chamber through a li uid sealing medium whichhas no aiiinity or the material, subjecting it to heat to drive ofl itscontained moisture and then passing the dried1 material out of thechamber through a sea This method may be practiced by the use of variousforms of apparatus, some of which are herein disclosed. in any'form,however, it is essential that the apparatus be provided with a closedchamber in which a partial vacuum may be maintained. In order that thematerial to be dried may be continuously passed through the vacuumchamber, the latter is provided with openings closed to the admission ofair by a liquid sealing medium which has no afiinity for the material.The liquid seal effectively closes the entrance. and exit passagesagainst the admission of air to 1 the chamber, but permits the passageof the material into and out of the chamber. The

form of the heating elements within the vacuum chamber, for drying thematerial, the

shape, form, dimensions and location of the liquid seal containers, andthe means for passing the sheet material through the charm er, may allvary.

My invention further relates to drying said sheet material by letting itpass adjacent to but not in contact with a source of convected heat,while under little or no ten sion, the tension being only suflicient topass the sheet material through the apparatus.

My invention further relates to passing said sheet material through saidvacuum chamber in folds or loops and subjecting one or more of the foldsor loops to the action of convected heat to dry said sheet material at alow temperature. My invention further relates to subjecting said sheetmaterial while in said vacuum chamber to the action of a glowing member.My invention further relates tosubjecting said sheet material while insaid vacuum chamber to an electric heating member, either in the form oflates or coils. My invention further relates to placing one or more ofthese electric heating elements adjacent to the folds or loops of thesheet material while passing through the vacuum chamber.

My invention further relates to manufacturing paper wherein the fibersin the paper are not weakened and the size if the paper has been sizedbefore drying, is not injured or damaged, due to the low dryingtemperatures at which I carry out my improved method.

7 My invention further relates to manufacturing colored paper and dryingit without substantially impairing the coloring matter and mordants usedin the paper. Among other advantages this insures that the paper Willhave bright colors which will be substan tially uniform in differentruns of paper, permitting matching of colored paper without anyappreciable difference in tone or color. I

My invention further relates to passing a web of wet paper, sized orunsized, into a vacuum chamber withoutbreaking the vacuum, and therepermitting the fibers of the paper to shrink and dry at random, forminga paper which is substantially as strong lengthwise of the sheet or webas across the said sheet or web.

My invention further relates to manufacturing imitation loi't driedpaper having a cockeled effect.

My invention further relates to taking a web of wet paper, either fromthe wet end of the paper machine, or from the sizing vat, or from acoloring apparatus, or coating or printing machine, and continuouslypassing the web of paper into and out of a vacuum chamber, withoutbreaking the vacuum in the chamber, and heating and drying said web ofpaper in said vacuum chamber by permitting the fibers to dry or shrinkunder little or no tension so as to obtain a'stronger and betterproduct. 1

My invention further relates to passing such web of paper adjacent tobut not in contact with one or more electric heating elements mounted inthe vacuum chamber.

My invention further relates to certain steps and combinations of steps,also to certain elements and combinations of elements,

whereby the method or processes herein described may be carried out, aswell as to certain details of construction and combinations all of whichwill be more fully hereinafter described in the specification andpointed Out in the claims.

I have shown in the drawings, somewhat diagraimmitically two differentforms of apparatus which may be used to carr out my improved method, butit is to be istinctly understood that my invention is not to be confinedto the particular form of apparatus shown by way of illustration.

In the accompanying drawings the same reference numerals refer tosimilar parts in the several figures.

Fig. 1 is a vertical "diagrammatic section of one form of apparatuswhich may be used to carry out my improved process;

Fig. 2 is a vertical diagrammatic section of a modified form in whichone seal is used instead of two;

Fig. 3 is a sectional view showing the termlnal wire connected with theelectric heater elements;

Fig. 4 is a sectional view of one form of regulator for rolls.

In describing my invention, I will describe it as applied to sheetmaterial in the form of paper, though it is to be distinctly understoodit is equally applicable to, and covers drying sheet material in theform of textile fabric, as for example drying'such fabrics after theyhave been washed, or bleached, or dyed, or otherwise treated with aliquid of some description.

In the ordinary drying of a web of wet paper such high heat is used asto injuriously affect the fibers of the paper, and in case the paper iscolored it will adversely affect the coloring matter and mordants used.Drying paper in the high temperatures used in ordinary practice oftenaffects the size so that the resulting paper varies in quality, is notuniform, and is not a perfect product.

In ordinary practice the paper is dried under sufiicient tension tocause the fibers of the paper to rearrange themselves which results in asheet of paper which is not uniform in strength.

By my improved method I dry the paper at such low temperatures, andwhile the paper is under practically no, or very little, tension so thatthe fibers can shrink at random, which action is not materiallyprevented by the very low tension on the paper while it is being dried.This results in much stronger paper and one which is substantially asstrong lengthwise of the sheet as it is crosswise of the sheet, thepaper being a much better product in every way.

My improved method can be employed for either manufacturing high or lowgrade paper, or imitation 10ft dried paper, having the same cockeledeffect as though the sheets had been cut, stacked and allowed to drslowl for forty-eight hours.

The we of paper 1, either coming from the wet end of a paper machine, orfrom a sizi'ng'vat, is passed into and out of the vacuum chamber 2 inany suitable manner so that the vacuum in the chamber will not bebroken. I have shown this vacuum chamber provided with seals 3 and 4 inwhich is a liquid medium 5 of any suitable material, which has noaffinity for, and no deleterious effect upon, the sheet 1, whatever itmay be.

The medium which I preferably employ is mercury though it is to bedistmctly understood that any suitable medium, having thecharacteristics above mentioned, may be employed. I may for example usean amalgam, or an alloy, or any other suitable material which willsatisfactorily seal the vacuum chamber 2 and permit the sheet material1, passing into and. out of said chamber 2, without being injured oraffected in any manner and without breaking the vacuum.

The degree of vacuum in the chamber 2 may be regulated. Preferably Iemploy a vacuum of about 28 inches, though this may so I,

be varied without departing from my invention.

The web 1 is fed into the vacuum machine over the guide roll 6. underthe submerging roll 7, over guide roll 8, and under the guide rolls 9, 9and over the guide rolls 10, 10. While passing through the vacuumchamber 2, it is ut under little or no tension; the tension 1ssufiicient merely to pass the web through the chamber. Preferably, theweb is fed through in folds or loopsll, 11.

Adjacent to the loops 11, 11, but not in contact with them, I mount oneor more glowing members preferably in the form of electric heaters 12,12. Preferably these electric heaters are mounted between the folds orloops 11, 11 as indicated in Fig. 1, but of course this arrangement maybe varied without departing from my invention. The electric heaters 12are connected to the bars 12", from which extend the wires 12, throughthe insulated packing 12, to the contact terminals 12. The distancebetween the folds 11, 11 and the electric heating members 12, 12 must besufficient to permit free passage of the web of paper without coming incontact with the electric heating elements.

To insure minimum tension upon the paper during drying, I may use anyordinary means to. decrease the tension due to moving the paper, as forexample, by mounting the various rolls. in each of the formsillustrated, in ball bearings, and drivin them by a friction devicewhereby the s ee of the rolls may be re lated. One orm of such deviceisillustra d'in Fig. 4 wherel in place by suitably packed bolts 32passing through the wall 2 of the vacuum chamber. The pulley 33,preferably made of bronze, is mounted on, and revolves on, the shaft 34of the roll 9. The portion of the shaft 34 upon which the pulley ismounted, is preferably made of Babbitt metal. Secured to the end of roll9 and the side of the pulley 33 are two friction discs 35 and 36, madeof any suitable material such as leather or woven asbestos tape. Thepulley 33 is driven at constant speed by a belt 37. The small roll 38 ismounted in a housing 39, the position of which is regulated by the lever40 actuated by the rod 41, passing through the packing gland 42 in thewall- 2. The position of the rod 41 is regulated by the nut 43. Theother end of the roll 9 will be mounted in a ball bearing housingsimilar to 31. The speed of roll 9 may be regulated, or its speed may bevaried from a similar roll, by varying the pressure between the discs 35and 36 by applying more or less pressure between the roll 38 and thepulley 33, which is driven at constant speed. As the friction betweenthe discs 35 and 36 increases, the more nearly will the speed of roll 9approach that of pulley 33.

The web of paper passing through the vacuum chamber will in this mannerbe dried, without placing any appreciable tension upon the web. Whattension, as previously described, there is upon the web, is merelysufficient to pass it through the vacuum chamber and this tension doesnot appreciably interfere with the fibers of the paper drying at random,so that the result ing sheet of paper is as strong lengthwise of thesheet as it is crosswise.

In, making imitation loft dried paper, this drying of the web within thevacuum chamber adjacent to, but not in contact with, theelectric heaters12, 12 and while under no appreciable tension causes the sheet or web todry with the cockeled effect of genuine loft dried paper.

The dry web of paper 1, whether it be high or low grade paper orimitation loft dried paper, after passing between the differcnt electricheaters 12, 12 is fed over the guide roller 13, and out of the vacuumchamber through the seal 4 under the submerging roller, 14, over theguide roller 15,

and is then preferably wound into a roll of finished paper 16.

In some cases, I may use one seal instead of two. I have shown such aconstruction in Fig. 2, in which the vacuum chamber 17 is provided withthe same electric heaters 12,

12 and the same guide rollers 9, 9 and 10, 10. Connected to the vacuumchamber is a hollow member 18, which dips into a liquid sealing member19. The liquid 5 in this sealing member is the same as in the seals 3and i.

The web 1 is fed into the vacuum chamber 17 over the guide roll 20 underthe submerging roll 21 and over the guide roll 22, and thence asindicated by the arrows, over anc'lunder the iderolls 9, 9 and 10, 10 onthe left of said figure, then over the guide roll 23 to the guide roll24, mounted at the other end of the vacuum chamber, thence over andunder the set of guide rolls 9 9 and 10, 10 mounted on the right of saidligure, all as indicated by the arrows, thence over the guide roll 25and out of said vacuum chamber through the liquid seal 5 under thesubmerging roller 26 over the guide roll 27, and is then preferablywound into the complete dry finished roll of sheet material 28. The"drying action in connection with the vacuum chamber 17 is the same asthe drying action invaeuum chamber 2.

The vacuum chamber 2 is preferably provided with the windows 29, 29 andwith the pipes 30, 30, which are connected to any suitable vacuumapparatus to maintain the desired vacuum within the vacuum chamber.

' When the sheet material is a web of paper, from which imitation loftdried paper is to be made, the web 1 is taken from the sizing vet andthen passed through the vacuum chamher in the manner previouslydescribed. When it emerges over the roller 15, it is dry, very strong,being substantially as strong lengthwise of the sheet as it is crosswiseof the sheet and has the same cockeled effect as regular loft driedpaper. It will be stronger than loft dried paper, however, for thereason that the fibers of the paper, as they originally came from thewet end of the paper machine in the form of a wet web of paper, werepreferably dried by my method prior to being sized. The fibers of thepaper were therefore, both when they were originally dried before beingsized, and also after being sized, permitted to dry or shrink at random,and while not under suificient' tension to prevent them fro-m so doing.

My method possesses many advantages not present in processes heretoforeused for many years in the drying of paper.

The evaporation process, which is characteristic of the so-ealled loftdrying of pa- 1 per, has many fully rcco nized disadvantages, and yet itis used tor lay and has been in use for many years. In this method thewet paper is taken from the paper machine,

cut into sheets, hung on oles, carried to the drying room where it 1ssubjected to hotair at about 130 F. for about 48 hours, and when dry,each sheet is separately calendered. Although possessing the advantageof drying at a comparatively low temperature, whereby the moisture isslowly evaporated, loft drying is obviously very ineilicient and costly,because it requires many separate manipulations, is extremely slow, usesextensive floor space and wastes heat.

- 28", the convection,

The process which is employed in the ordmary paper machine in commonuse, is likewise subject to many disadvantages. In such machine, the wetpaper as it comes from the paper machine, is passed over many revolvingcylinders, heated internally by steam to sufiiciently high degree ofheat, to raise the temperature of the water in'the paper to 212 F.. theatmospheric boiling polnt of water. It is customary to supply the dryingcylinders with steam at approximately 5.3 pounds gauge pressure, atwhich the steam has a temperature of 228 F., giving a difference oftemperature (228-212) of only 16 F. With this slight difference oftemperature the transfer of heat is extremely slow, and hence it isnecessary to employ, many drying cylinders, in board machinesoften onehundred, and'in news.

print machines,'forty or more.

Also due to convection and conduction losses, as well as those incidentto leaks in the piping system and other inefliciencies, the heatactually'required for atmospheric drying of a ton of wet paper, is verymuch in excess of the theoretical requirement. The thermal efliciency ofatmospheric drying by steam heated cylinders is therefore very low.duced from boiling the water out of the paper, is driven ofif into theoperating room, and although fans and exhausters are employed, at largeexpense for power and maintenance, the room atmosphere is so constantlysaturated with moisture as to rust and ultimately destroy all iron andsteel materials, and produces an exceedingly disagreeable and unhealthyatmosphere in which to work. It is well known that the minimumtemperature 212, the atmospheric boiling point of water, is positivelyinjurious to, and results in oxidizing, the fibres of the paper, thestrength of which is vastly improved when the paper is dried at lowertemperatures, as in loft drying. This atmospheric drying processrequires large initial cost for cylinders, felts, and other necessaryequipment, and extensive floor space, and results in the consumption oflarge amounts of power, and great cost for operation, maintenance andrepairs.

The thermal efiiciency of my vacuum method is very much greater thanthat of the atmospheric cylinder drying heretofore in universal use fordrying paper. Theoretically, it requires about 5287 pounds of steam todry one ton of paper at atmospheric pressure, but to compensate forconvection and conduction losses, and those due to leaks in the pipingsystem, and other inefiiciencies, it has been shown in practice thatabout 10,600 pounds are required.

In my method, using a vacuum of about conduction and piping losses areexceedingly small and. the total Furthermore, the steam pro-' steamrequired to dry a ton of paper by my method is approximately 5200pounds.

It is an established fact that paper dried at low temperatures is muchstronger than when it is dried at the high temperatures used in papermachine atmosfpheric drying.

Paper dried in a vacuum 0 8", or at a temperature of about 100 F., as inmy met 10d, is very much stronger than paper dried at atmosphericpressure, when the steam in the driers is at 228 F. When paper is driedby myp; method, therefore, a cheaper furnish or stock can be used andstill produce a paper equal in strength to atmospheric dried paper, inwhicha hi her grade furnish or stock is used. In ma ing newsprint paoer, I am able to dispense with a considerab e portion of the moreexpensive sulphite pulp, as this can be replaced with the cheaper groundwood pulp.

-Furthermore, in my method there is a great saving of heat (or steam)because the process is carried on in a vacuum chamber which acts on theprinciple of a thermos bottle, and the steam and vapors driven out ofthe wet pa )er are caught in the closed vacuum cham er, and conductedaway to the condenser. "The operating room is free from steam, humidityand heat, and fans, and exhausters are dispensed with. In the useof mymethod the a paratus is at all times operating under de nite humidity,the control of the drying can be closely standardized, and the moisturecontent in the paper carefully regulated.

Having; pointed out the many advantages of my method and apparatus overthose heretofore used, it will be apparent that the use of my inventionresults in great economy in the initial cost of apparatus and in largesavings in cost of operation, maintenance and repairs.

Having thus described this invention in connection with an illustrativeembodiment thereof, to the details of which I do not desire to belimited what is claimed as new and what is desired to secure by LettersPatent is set claims.

What I claim is 1. The method of drying a continuous web of paper comingfrom the wet end of a paper machine or from a sizing vat or from acoloring a paratus, coating machine or printing mac ine, consisting incontinuously feeding the web of paper into and out of a vacuum chamberwithout breaking the vacuum, and without suflicient tension upon the webto cause its fibers to substantially rearrange themselves from theinterlaced position assumed by them on the wire mesh of the papermachine, subjecting said web on its continuous passage through thevacuum chamber to radiant heat from an electric heater, so that the webof paper will be dried with its forth in the appended fibers insubstantially the interlaced-position assumed by them on the wiremesh ofthe paper machine. Y

2. The method of drying a continuous web of paper coming from the wetend of a paper machine or from a sizing vat or from a coloringapparatus, coating machine or printing machine, consisting incontinuously. feeding the web of paper into and out of a vacuum chamberwithout brcaking'the vacuum, and without suflicient tension upon the webto cause its fibers to substantially rearrange themselves from theinterlaced position assumed by them on the wire mesh of the papermachine, subjecting said web on its continuous passage through thevacuum chamber to-ra-diant heat from an electric heater, so that the webof paper will be dried with its fibers in substantially the interlacedposition assumed by them on the wire mesh of the paper machine and thenwinding the dry web of paper into a roll vacuum chamber through one ormore merv cury seals and during its passage through placing onlysufiicient tension upon the web to insure its continuous passage, thetension not being sufiicient to cause'its constituent fibers tosubstantially rearrange themselves from the interlaced position assumedby them on the wire mesh of the paper machine,

said vacuum chamber and mercury seals and continuously heating anddrying said web while in said vacuum chamber by causing it to traveladjacent to but not in contact with one or more fixedelectric heaters.

OGDEN MINTON.

